Telephone and direct conversation circuits



April 1934- w. L. HARRIS 1,954,932

TELEPHONE AND DIRECT CONVERSATION CIRCUITS Filed Aug. 30, 1932 INVENTOR W. fiEwW Jw BY Kw:

/ ATTORNEY Patented Apr. 17, 1934 TELEPHONE AND DIRECT CONVERSATION CIRCUITS Walter L. Harris, Omaha, Nebn, minor to American Telephone and Telegraph Company, a corporation of New York Application August 30, 1932, Serial No. 631,086

7 Claims.

This invention relates to improvements in telephone circuits and more especially to rendering such circuits of greater use to those of impaired hearing whereby at a subscriber'station they may 6 have not only the benefit of amplifying means for telephone conversation but may also be 'able to carry on direct conversation with others, making use of the same circuit elements and amplifying means.

10 The purpose, more specifically, is to use the present telephone circuits of subscriber sets either for telephone conversation or for direct conversation, whereby the latter term is meant conversation between two persons near each other.

l5 In general one of these is a person who has such impaired hearing as to require aid of some form. Such aid may be through the inherent .amplifying properties of telephone transmitters or, in addition, may comprise certain other amplifyng means such as the well-known vacuum tube amplifiers.

Another purpose of this invention is to combine with the use of a vacuum tube amplifier which is already available for amplifying incoming telephone conversations its use for di rect conversation by so rearranging the circuit at will as to adapt the equipment of the 'subscriber set for such direct conversation.

The invention will be better understood by reference to the following specification and the accompanying drawing in which Figure 1 shows in, simplified form one method of rearranging the circuitto permit of its use for direct conversation, this circuit relating more specifically to a local battery talking, common battery signaling subscriber set. Fig. 2 shows a modification adapted for common battery telephone circuits and at the same time this figure shows in greater detail the elements which go into a subscriber station equipped with a vacuum tube amplifier.

Referring more specifically to Fig. i, there is shown an incoming line Ll connected to a subscriber set of which the only parts shown are the ringer circuit 2, an induction coil 3 with local battery 4, and three terminals going to the remainder of the station equipment ina manner to be shown and more fully described in connection with Fig. 2. In order to rearrange the cir- 5o cuit for direct conversation a break in the line is made at 0-12 and additional connections as shown in dotted lines are introduced at this break. These connections include the key S which in the one position closes the gap from (1 to b leaving the circuit as before in condition for telephone conversation. In its second position the key eflectivelydisconnects the line L1 and the ringer circuit 2 from the subset and bridges across the.subset from b to c an impedance element 6 which, if desired, may be a short circuit or a pure resistance of any desired magnitude.

Upon the removal of the receiver from its switchhook and with key S in its second position. a person may speak into the microphone. and one of impaired hearing will find substantial'aid by listening at the receiver, advantage being taken of the inherent amplifying properties of a microphone. In addition to this, an amplifier 7 such as a vacuum tube amplifier may be provided, all in the manner to be described more fully in connection with Fig. 2.

In its normal condition the impedance of the line as seen from the subscriber set is such that the amount of side tone in the telephone receiver, particularly in case of anti-side tone sets, is lower than is desirable for purposes 'of direct converse! tion. If, however, a short-circuit should be connected from b to c then the unbalance introduced would be such as to substantially increase the side tone thus rendering the set more eflicient for direct conversation. However, in place. of making a short-circuit from b to c, it may be convenient to control the amount of side tone by adjusting the impedance of the element 6 until the desired eifect is produced.

Referring more specifically to Fig. 2, there is shown a circuit adapted for common battery operation, and for aaperson who needs no special aid the circuit is one characteristic of a common form of subscriber set with anti-side tone characteristics. Upon removal of the switchhook, hereafter referredto as H, the circuit is closed 1 at the points HI. and H2 and the hand-set 9, comprising receiver wand transmitter 11, is connected in circuit, all in a manner well-known in p the art.

input circuit of the vacuum tube 20, the output 110 of whichincludes the transformer T2 with its primary winding 21 and secondary 22. The operation of the key A transfers the receiver 10 at the point A2 from its former position to that of a series connection with secondary 22. The operation of the vacuum tube is controlled by relay contacts 26 in the filament circuit. These contacts may be closed by a relay 2'? normally supplied by current from the common battery.

When the key A is in its non-operated position the switch point As is closed and this places a direct short-circuit across the relay 27. When, however, the amplifier is to be used, operation of the key A will close the switch at A1, transfer the receiver by the switch A: to the output of. the amplifier, open switch A: and close the contacts 26. With this connection, one of impaired hearing may listen to an incoming telephone conversation through the amplifier.

Usually such a person will have such impaired hearing as to require aid in direct conversation with someone in the room. Such direct aid may be obtained by operating a key, hereafter referred to as D, with switch points D1, D2 and Da. The operation of this key will disconnect the line L1 and ringer circuit 2 and will introduce in its place a battery 30 and resistance or other impedance element 31. This will leave the ringer connected to line and receptive to incoming calls.

.The transfer will so unbalance the circuit as to introduce a large amount of side tone in the receiver 10 and a person speaking into the, transmitter 11 will be heard in the receiver 10. The amount of side tone introduced may be adjusted to a desired value by the impedance element 31. The connection is such as to permit direct conversation whether the key A is in its operated or non-operated position. In the latter case the amplifier is not in use and reliance is placed on the amplifying characteristics of the transmitter. If the key A is'operated then the amplifier is introduced as previously described. The battery 30 is used to supply the direct current for the set which would otherwise come from common battery.

In case the subscriber set is supplied with a handset the receiver and the transmitter will be so close that a second party cannot conveniently use the transmitter. For this reason I find it desirable to supply an additional transmitter 12 which may be substituted for the transmitter 11. This is conveniently accomplished by associating the previously mentioned switch D], with switches D: and D3 into a single key' referred to above as the key D. Such additional transmitter or transmitters could also be used in the circuit of Fig. 1. While the diflerent switches may be associated separately or in any other manner, I find it convenient to combine certain ones for simple operation thus, as stated above, the switches D1, D2 and D3 may be combined into a single key; A1, A: and A: may be combined into another single key A, and H1 and H: would be combined to constitute the switchhook in the usual way. It will thus be seen that with keys A and D in nonoperated position and the receiver off the hook the subscriber set works in a normal manner. A person of impaired hearing would operate key A thus introducing the amplifier. When direct conversation is. desired the receiver is removed from its hook and key D is operated whereupon transmitter 12 is substituted for 11. If additional aid is required, and thiswould usually be the case for a person of impaired hearing, key A is operated whereupon the amplifier is introduced.

2. In a telephone system comprising a line and a telephone subscriber set with a transmitter, a

receiver and a ringer circuit, means for disconnecting the transmitter and the receiver part of the circuit from the line and leaving the ringer circuit operatively connected to the line, said means connecting a bridging member across the subscriber set whereby the local circuit is connected for efficient direct conversation from the transmitter to the receiver and the ringer remains operative to incoming calls to the line.

3. In a telephone system comprising a line and a telephone subscriber set with a transmitter, a receiver and a ringer circuit, means for disconnecting the transmitter and the receiver part of the set fromthe line and leaving the ringer circuit operatively connected to the line, means connecting a bridging member of adjustable impedance across the disconnected portion of the subscriber set, whereby the set is connected for emcient direct conversation from the transmitter to the receiver and the ringer remains operative to incoming calls from the line.

4. m a telephone subscriber set with a transmitter and a receiver=adapted for a connection to a telephone line, an amplifier, means for connecting and disconnecting the amplifier at will without aifecting the response to outside calls, means for disconnecting the subscriber set from the line at will, said last named means rendering the circuit suitable for direct conversation from the transmitter to the receiver.

5. In a central station telephone system, a line and a subscriber deaf set equipment comprising a subscriber set and an amplifier, means for connecting or disconnecting the amplifier at will, a local battery and a switch adapted in the one position to connect the set to the line and in the other position to replace the line by the local battery, whereby the set is connected for direct conversation with or without the amplifier. v

6. In a central station telephone system, a line and a subscriber deaf set equipment comprising a subscriber set and an amplifier, means for connecting or disconnecting the amplifier at will, a local battery and a switch adapted in the one position to connect the set to the line and in the other position to-replace the line by the local battery and to introduce a supplementary transmitter, whereby the set is connected for direct conversation either with or without the amplifier. 7. In a central station telephone system, a line and an anti-side tone subscriber set comprising the subscrlber set and an amplifier, means for connecting or disconnecting the amplifier at will, a local battery and a switch adapted in the one position to connect the set to the line and in the other position-to replace the line by the local battery to introduce large side tone, whereby the set is connected efllciently for direct conversation either with or without the amplifier. WALTER L. HARRIS. 

